The present invention relates to a lightable indicator scale device, and, in particular, a lightable indicator scale device for a combination instrument in a motor vehicle, having a dial which has a first lightable indicator scale in a first area, a second lightable indicator scale in a second area and a third lightable indicator scale in a third area.
FIG. 2 shows a top view of a conventional lightable indicator scale device for a combination instrument in a motor vehicle, and FIG. 3 shows a cross-sectional view of the conventional lightable indicator scale device illustrated in FIG. 2.
FIGS. 2 and 3 show a first lightable indicator scale 1 in the form of a km/h scale, a second lightable indicator scale 2 in the form of a cruise control scale, a third lightable indicator scale 3 in the form of an mph scale, beams of light L1-L3, a system carrier 4, a luminous disk or diffusing panel 5, a liquid crystal display 6, a cold cathode fluorescent lamp 7, a dial 8 and a polarization filter 9.
With the lighting for the two concentrically arranged indicator scales 1 and 3 in the combination instrument with cold cathode fluorescent lamp 7, the cruise control segments between these two scales must be selectively switchable between lighted and unlighted.
Guarantee this, German Patent Application 195 47 375 A1 describes that all three indicator scale 1, 2, 3 can be lighted with a single light source 7 as illustrated in FIG. 3. In system carrier 4, which simultaneously functions as a reflector, cold cathode fluorescent lamp 7 is located beneath luminous disk 5 with liquid crystal display 6 above it, the latter being controllable locally in the area of the cruise control scale. The cold cathode fluorescent lamp 7 lights up all three indicator scales 1, 2 and 3, as illustrated by beams of light L1, L2 and L3 passing through corresponding transparent or translucent passages in dial 8 to the observer.
Two polarization filters 9 are arranged in the area of cruise control scale 2. They are crossed so that no beam of light L2 passes through cruise control scale 2 to the observer when liquid crystal display 6 is not activated, so that cruise control scale 2 appears dark in the respective indicator segment.
Selective activation of individual areas of liquid crystal display 6 corresponding to the cruise control indicator segments makes it possible for incident beam of light L2 to undergo a change in its polarization in the area of liquid crystal display 6 and thus be able to pass through crossed polarization filters 9, so cruise control scale 2 appears bright in the respective indicator segment.
A disadvantage of the above described lightable indicator scale device is that the shape of liquid crystal display 6 must be adapted to that of cruise control scale 2 (a horseshoe shape in the example illustrated here) and therefore this display is complicated, sensitive and expensive to manufacture, and both installation and removal are complicated.
A lightable indicator scale device according to the present invention has an advantage in that expensive liquid crystal displays which have complicated shapes, such as semicircles, can be eliminated for light control of the cruise control indicator segments and can be replaced by a simple independent second light source device which is expediently provided only for the cruise control scale. For example, LEDs (light emitting diodes) employing a simpler and less expensive control concept in comparison with a liquid crystal display may be used for this purpose.
The present invention contemplates that a light guide device is provided between the first and second light source devices, on the one hand, and the dial, on the other hand, to split the light of the first light source device, i.e., the cold cathode fluorescent lamp, into the first and third areas, which are separated by the dark second area which is free of scattering. This second area corresponding to the second indicator scale can be used for displaying information with the second light source device which is separated from the first light source device.
In one embodiment, the second lightable indicator scale is arranged between the first lightable indicator scale and the third lightable indicator scale, and all three indicator scales are substantially concentric.
In another embodiment, the first light source device is a cold cathode fluorescent lamp.
In another embodiment, the second light source device is an LED arrangement, which can be controlled easily to selectively light indicator segments of the second indicator scale.
In another embodiment, the first lightable indicator scale is arranged substantially in front of the first light source device, and the third lightable indicator scale is offset to the side from the former.
In another embodiment, the first light source device is toroidal, the axis of the cylinder arranged substantially normal to the viewing direction, and the light guide device adjacent to the first light source device has a corresponding semicircular first cutout adjacent to the first light source device. This symmetry permits a relatively simple design of the light guide device.
In another embodiment, the light guide device has a triangular second cutout adjacent to the dial. The light guide has an edge which prevents beams of light from the first light source device from reaching the second indicator scale directly.
In another embodiment, the light guide device has substantially plane-parallel surfaces in the second area. This prevents input of light from the first light source device into the second indicator scale, on the one hand, while, on the other hand, preventing input of light from the second light source device into the first or third indicator scale.
In another embodiment, the light guide device has a chamfered area in the third area for output of beams of light for lighting the third lightable indicator scale. This area, which is preferably stepped, ensures complete output of light at this point into the third indicator scale.
In another embodiment, a system carrier is provided to hold the dial and the light guide device.
In another embodiment, the system carrier functions as a reflector for the first light source device in the first area.
In another embodiment, the system carrier has a lighting well for the second light source device in the second area. It is possible to obtain from the second light source device a directional or collimated light beam traversing the light guide device essentially in a straight line to reach the second indicator scale, i.e., the respective indicator segment of the cruise control scale.
In another embodiment, the light guide device has a surface which is inclined so that incident beams are either allowed to pass through to the first indicator scale or are deflected by total reflection such that they undergo total reflection again in the second area and thus do not light the second indicator scale.